<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
       /* div{
           float: left;
           width: 200px;
           height: 200px;
           border: brown 1px solid;
           margin-bottom: -1px;
           margin-right: -1px;
       }
       .zz{
           margin-right: -2px;
       }
       .vv{
           margin-left: -2px;
       } */
    div{
       width: 0; 
       height: 0;
       line-height:0;
         border: 10px solid  transparent;
      border-top: 10px solid red;
     /* border-right: 10px solid green;
      border-bottom: 10px solid blue;
       border-left: 10px solid #000;  */
}

    }
    </style>
</head>
<body>
     <!-- <div class="zz"></div>
     <div></div>
     <div></div>
     <div></div>
     <div></div>
     <div class="vv"></div> -->
     <div></div>
</body>
</html>